I. Definition of time

Dividing Lines:
In the game, there are three types of divider lines: thin lines, thick lines, and thick lines which are even thicker at the edges (I'll call them huge lines).

Measures:
We will define a measure as the time represented between two consecutive huge lines. Each measure is divided by a certain number of thick lines representing beats within the measure. And finally each beat is divided in half by the thin lines.

Time Signatures:
This definition of a measure implies time signatures. In standard notation, a time signature is represented as X/Y where Y defines the type of division that is considered a beat (4 = quarter notes, 8 = eight notes, etc.), and X defines how many of those beats are contained in each measure. For example, 4/4 means 4 quarter notes per measure, 6/8 means 6 eighth notes per measure, etc. The most common time signature is 4/4, although there are some songs containing 6/8 and 3/4. As far as we're concerned, X is used to determine how many thick lines are placed between huge lines, and Y has no meaningful information within the game (we don't care if a beat is actually a quarter note or an eighth note within the song).

Hopefully all this will make the following explanations clear.

II. Basic Note Scores

The only question is notes that you hold. The initial note still gives you the same 50 points, but for every beat [defined above] that you hold it, you receive half of the initial value, or 25 points. This will, of course, scale to the base value of the note/chord (if it's a held chord, then you would earn 50 points per beat).

Example: The first held note in Iron Man - Easy. As you can see on the note charts, the first note is held for just under 8 beats. If you test this, you'll see that you receive 247 points after playing the hold. 50 (initial) + (8 beats * 25 points per beat) = 250 points, minus a few points because the hold ends before the 8th beat is over = 247.

Note: If the calculated "hold points" for a note is not an integer, it is rounded to the nearest integer (such that x.5 rounds up).

III. Multipliers

Multipliers do exactly what you think they do. They multiply every point value by the number indicated. So, at 4x, every single note is worth 200, and chords are worth 400.

When you miss a note or strum an incorrect note, your streak (and thus your multiplier) vanishes. As you build your streak back up, your multiplier will increase every 10 notes. So, in terms of your streak:

Chords do not count as two notes when building up a streak. Thus, on a high difficulty of Unsung, it takes 30 chords to get back your x4. Math prodigies will realize that your mistake cost you twice as much--6400 points.

But wait. What about holds?

Holds obviously don't increase your streak, but they are worth more points. So, let's take an example where you only play chords, and hold them each for one measure.

This must be where math is useful in the real world, just like my algebra teacher claimed. I think I just lost a 10-year-old $20 wager.

IV. Acquiring Star Power

Yay, star power. The little blue meter on the right. You must have half the bar to activate it, and each time you gain star power by playing a correct sequence, you get 1/4 of the bar. So, hitting two star power sequences will always give you enough to use it.

The only variable is star power sections that have holds, where you can whammy for extra power. Star power is gained at a rate of 3.3333% of the meter per beat. This means the following:

Whammying for 7.5 beats will gain 1/4 of the star power meter
Whammying for 15 beats will gain 1/2 of the star power meter
Whammying for 30 beats will gain the entire star power meter

Note: In GH2's co-op mode, star power is acquired at a slower rate, as follows:
Whammying for 10 beats will gain 1/4 of the star power meter
Whammying for 20 beats will gain 1/2 of the star power meter
Whammying for 40 beats will gain the entire star power meter

Note that this star power explained above is only what is gained from whammying and does not include the 1/4 meter that you can additionally gain from completing star power sequences.

The best example I can give is the opening note of Iron Man.

We've already established that this first note is just shy of 8 beats (and longer than 7.5 beats). Obviously, playing the note itself gives you that initial 1/4 of a meter for playing the "whole sequence" (1 note) correctly. This means (based on the rates above), you need to whammy an additional 7.5 beats to gain abother 1/4 meter to get up to half your bar. So if you begin whammying at the beginning of this note, you will reach 1/2 a meter just before the hold ends.

One more thing: it doesn't matter how fast you whammy. As long as you have it activated (ie: the note turns blue while you whammy), you're gaining star power at a constant speed (3.3333% per beat).

V. Using Star Power

To use star power, tilt the guitar up or press the select button. Once you activate it, it runs for a specific amount of time before it expires, and doubles your current multiplier.

The amount of time it lasts is based on measures, and the amount of star power you have (duh).

Note: In GH2's co-op mode, star power does not last as long and the following rules apply:
A half filled star power meter lasts 3 measures.
A completely filled star power meter lasts 6 measures.

Note: This star power duration is based on measures, not beats. The number of beats that a star power will last is dependent on which time signature you're playing in (in another words, how many beats are in a measure).

I'll use two examples to illustrate.

1) Ziggy stardust (use the note chart∞ to help you visualize). You can get a full star power bar built by the time the first flurry of chords come (I'm looking at hard or expert). If you activate star power exactly when the first Yellow+Orange chord sequence arrives, it will run out right when you return to the original G+Y chord. This is 8 measures long (32 beats because we're in 4/4 time, 4*8 = 32).

2) Iron Man. I choose this song because it changes tempo during the solo, and near the end. If you look at the note chart∞, you'll see that the lines become much closer together during those times. I tested by using star powers both during the normal tempo, and during the fast tempo. In both cases, the length was determined by the measures.

So, star power will run out faster (measured by seconds) during times where the tempo is faster. Similarly, in songs where the beat is always very fast (Callout, Breaking wheel), star power seems to vanish quickly.

3.) The Breaking Wheel. This song contains time signature changes, continuosly switching between 6/8 and 4/4, so this is a very important example in understanding how star power usage is determined. You can view the note chart∞, but it does not indicate the time signature changes. To see the changes you can play the song and count the number of thick lines between the huge ones. You'll notice it begins with 6 beats (thick lines) per measure and changes to 4 beats per measure, and the changes repeat several times. If you build up a entire star power meter (8 measures worth), and activate it with 3 measures of 6/8 remaining before it changes to 4/4 for at least 5 measures. Then the star power will still last exactly 8 measures, (3 in 6/8 = 18 beats) + (5 in 4/4 = 20 beats) = 38 beats. In this case, star power lasted 38 beats, but this could change depending where you use the star power.

So, in the above example, the star power meter actually drains slower in the 6/8 section and faster in the 4/4 section even though the tempo remains constant.

An important distinction:Acquiring star power by whammying is based on beats (doesn't care about time signature).The duration of star power is based on measures (dependent on time signature).

VI. Rating System

Now to answer the big question: how does the game assign my star-rating?

I'll begin by saying that you can only achieve ratings of 3-stars, 4-stars, and 5-stars (there is no such ratings for 1-star or 2-stars).

The ratings the game assigns are directly related to your score. This means there exists a score "cutoff" for achieving 4-stars and another cutoff value for 5-stars, such that:

1.) If your score is greater than or equal to the 5-star cutoff, you earn 5-stars.
2.) If your score is greater than or equal to the 4-star cutoff and less than the 5-star cutoff, you earn 4-stars.
3.) Otherwise you get 3-stars.

Now you may wonder, how are these "cutoffs" determined?

After gathering and processing tons of data, we've derived the answer.

It's based on the total number of points that a song contains. If you add up all the points possible from each note/chord and its hold points (if any) assuming a 1x multiplier the entire time, you'll get a total which I'll refer to as the "base_score" for the song.

Using this "base_score", the cutoffs are a result of a very simple calculation:

Where combined_medium_base_score is the sum of the base scores for lead and either rhythm or bass on medium, and similarly for expert.

This means that in single player, in order to achieve 4-stars, you must average a 2x multiplier throughout the song. And similarly, you must average 3x (or 2.8x in GH2) to earn 5-stars. Keeping in mind the fact that missed notes are equivalent to 0x (not 1x, since you don't gain any points).

VII. FAQ

Does the whammy bar increase the points gained on long notes?

- No. Test it on the first note of Iron Man.

Does the difficulty affect the scoring system?

- Nope. Higher scores are possible when there are more notes, but scores are calculated the same way.

Does tilting the guitar affect the scoring system?

- Other than the fact that it is used to activate star power, no. You gain the same amount of points regardless whether the guitar is tilted or not.

I know I missed a note, why does it say 100%!? Does the game round up?

- No, the game does not round up for "% Notes Hit". Even if you miss a single note in a song with over 1,000 notes, it would still indicate 99%.

- If you know you "missed" something but it still says 100%, this means you hit all the notes in the song, but also strummed an extra time somewhere between notes breaking your note streak and restarting your multiplier.

Let me know if this FAQ is helpful, and if you have additional questions post them here and I will update the FAQ.